I've been using their drivers for 5 years now, starting with AGP-based cards. My current card in the notebook is PCI Express based and lightning fast with the driver. My Gnome session is fast on a 1920x1200 screen and DVDs through Totem and MPlayer play flawlessly. NWN runs fine and without screen glitches (on the current release) although occasionally a driver release will introduce a small bug.
All-in-all NVidia are much better than ATI in terms of Linux support and their stuff just works (previous drivers are usally available if you need to roll back).